Screening apparatus



June 1, 1937. w. ROSS 2,082,302

S CREENING APPARATUS Original Filed March 27, 1931 Ros Patented June 1, 1937 UNITED STATES PATENT oFFIeE Continuation of application Serial No. 525,775,

March 27, 1931.

This application June 14,

1935, Serial No. 26,673. In Great Britain February 26, 1931 4 Claims.

This invention relates to screening apparatus of the kind comprising screening members spaced apart in parallel relationship and over which the material moves in a direction transverse to the screening members.

In known apparatus of the above kind it is usual to employ more than two screening members which are rotated, in the same direction and at successively increased speeds from the feed end, such that some individual screening members exert both downward and upward tractive forces on the material, the downward tractive force of said individual screening members tending to push the material into screening apertures in part formed by said screening members on one side thereof (which downward force is therefore detrimental to the success of the screen) and the upward tractive force tending to eject the material from other screening apertures in part formed by the said individual screening members on the opposite sides thereof (which upward force is therefore useful).

Thus in the known screening apparatus any variation in the upward tractive force of individual screening member which performs the two functions above mentioned must result in a similar variation in the downward tractive force of this member. That is to say, it is impossible to increase the upward and useful tractive force of such a screening member without effecting a corresponding increase in the downward and detrimental tractive force thereof and conversely this latter force cannot be diminished without a corresponding diminution of the former force.

It is the object of this invention to provide screening apparatus of the kind first above referred to wherein it is possible to vary the upward and useful tractive force of a screening member independently of any variation in a downward and detrimental tractive force as above defined.

In the drawing,

Figure 1 is a sectional side elevation of one embodiment of the invention.

Figure 2 is a plan of Figure 1.

Figure 3 is an end elevation of Figures 1 and 2.

Figures 4 and 5 illustrate modified forms of the apparatus illustrated in Figure 1, and

Figure 6 is a part fragmentary plan of a further modification.

Referring to the drawing, in Figures 1 to 3 there is shown a screening apparatus comprising a pair of elements 2, 3 of which the element v59 between them which constitutes the sole screening aperture since the pair of rollers form a screen unit and except for this aperture 59 the rollers have no relation with any other screening aperture. Further, as will be clearly observed in the drawing, the shortest distance between the two rollers lies in a horizontal plane.

Whether the screen member 2 is rotated or fixed the downward force exerted upon the material is less than the upward force exerted thereon by the roller 3 which may be rotated as quickly as desired since the other side of this roller bears no relationship to another screening aperture as is the case with existing screens where a, single roller combines with other rollers to form screening apertures on its opposite sides.

The material to be screened is fed on to the roller 2 by an inclined feed plate 6 and that which does not pass through the screening aperture 50 into the hopper 54 is discharged from the roller 3 on to a further inclined plate 5a the forward edge of which is arranged close to the discharge side of the roller 3 and substantially below the axis 4 of the roller so that material discharged from the latter must fall on to the discharge plate and cannot pass between the. same and the roller 3.

The element 2 is carried at its ends upon blocks 5| slidable upon spaced girders I underthe control of adjustment screws 52 passed through angle plates 53 fixed to the girders I. It is thus possible by actuation of the screws 52 to vary the size of the screening aperture.

Referring to Figure 4 the element 2 of the previous embodiment is substituted by a quadrant I! which is mounted for oscillation about its shaft l8 within limits set by stops or springs (not shown) in order that the size of the screening aperture 50 may be adjusted.

Referring to Figure 5 the element 2 of the first embodiment is substituted by a fixed plate I9 which is mounted for movement towards and away from the roller 3 in order that the size of the screening aperture 50 may be varied.

The screen elements 2, 3 may be formed with conical surfaces so that the screen aperture is composed of a series of narrow apertures 2| (Figures 2 and 6) appropriately termed fines apertures and comparatively wide apertures 22 which are formed between the narrow apertures in a direction longitudinally of the bars.

Referring to Figure 6 the screen element 2 is mounted upon bars 23 carried upon screw rods 24 which pass freely through fixed blocks 25 and carry on either side of the latter nuts 26, 21 between which and the blocks 25 there are provided springs 28, 29 surrounding the screwed rods. The screen element 2 may thusbe moved towards and away from the other screen element 3 in order to adjust the size of the screen aperture while the springs provide a resilient mounting for the screen element 2 which absorbs sudden shocks during screening and enables slight automatic adjustment of the screen aperture.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

1. Apparatus for screening hard unbreakable material, such as coal and rock material, comprising in combination a pair of co-operating screening elements spaced apart in parallel relationship to form a screening aperture only between them. (the two screening elements having no screening eifect as regards any other screening aperture) one said element upon which the material travels first having a smooth surface which is steeply inclined downwards with respect to the screening aperture and extends well beneath the latter and the other said element being constituted by a roller, ribs extending throughout the entire length of said roller, said ribs being so widely spaced circumferentially as to permit pieces of material just over the size of the aperture to enter the space between the two elements, but upon failure of passing through this space the next oncoming rib will jerk this oversize piece of material upwards, the ribs projecting only slightly beyond the roller surface so as to cause no interruption to the flow of the small material and the element with respect to the other element.

3. Apparatus as claimed in claim 1 comprising a downwardly inclined discharge plate adjacent the discharge side of the rough surfaced element and having its upper edge disposed close I to the said, element and well below the longitudinal axis thereof.

4. Apparatus for screening hard unbreakable material, such as coal, stone and rock material, comprising in combination a pair of screening elements spaced apart in parallel relationship to form a screening aperture only between them (the two screening elements having no screening eifect as regards any other screening aperture), means for feeding the material to the screening aperture in a direction transverse to the longitudinal axes of the screening elements, the one said element nearest the feed side, and with which the material to be screened engages first, having a smooth surface which is steeply inclined downwardly with respect to the screening aperture and extends for a substantial distance below the aperture and the other said element being constituted by a roller rotated in a direction whereby the portion thereof presented to said screening aperture moves upwardly, and ribs extending throughout the entire length of said roller and spaced circumferentially thereof which subject over size pieces of material lying at any point within said aperture to a series of upward jerking movements.

, WILLIAM ROSS. 

